A distance measuring apparatus is known which allows pulsed light to bounce back and forth between a distance measuring apparatus and a measurement object, and measures time required for its round trip to measure the distance to the measurement object (see patent document 1, for example). In this apparatus, when pulsed light reflected by the measurement object is detected, signal is amplified through an amplifier, and the shorter the round-trip time of the pulsed light, the smaller the gain of the amplifier is set. For this reason, short-distance can be measured while avoiding the saturation of the amplifier, and thereby short-distance to long-distance measurement can be performed accurately. As an amplifier capable of gain adjustment as described above, for example, an automatic gain control (AGC) amplifier, a sensitivity time control (STC) amplifier, or the like is known.
In addition, when strong reflected light from a measurement object enters a receiver, an input voltage of an amplifier may suddenly increases to a specified value or more. In this case, there is a case that much time is required before the voltage of the amplifier stabilizes again to a region where the amplifier functions normally, and during this time, the receiver becomes unable to receive reflected light normally. This state is the saturation of the amplifier.
Patent Document 1: Japanese Unexamined Patent Application Publication No. Hei7-71957